The present invention relates to an apparatus for manufacturing a printed circuit board (PCB), and more particularly to an apparatus for forming a circuit pattern and throughholes on a PCB in accordance with data based on a CAD.
There is a case where a small number of PCBs are manufactured for the development of an electronic equipment and the manufacture of a small number of electronic equipments. Even if such a small number of PCB is made, it is desirable to be able to accurately and quickly produce an inexpensive PCB. In such a manufacturing process, optical and chemical processing steps for which a negative for each circuit pattern is required. Since it is necessary to provide the negative even though the number of the PCBs manufactured therewith is small, the manufacturing operation is complicated.
More particularly, in a PCB where circuits are formed on both sides of the substrate thereof, throughholes connecting the both sides are perforated so as to provide a connection between the circuits. Such a PCB with throughholes is also advantageous in that the leads of electronic devices can be passed through the throughholes.
However, the throughholes require complicated processes after the holes are formed, such as plating of the inner surfaces with copper, or filling the holes with silver paste and baking.
In order to simplify the manufacturing process, there has been proposed a print circuit copper laminated board, which is often called a copper film substrate and referred to in the present specification as a PCB substrate, having an insulating substrate on which copper layer is laminated. The PCB substrate is machined to form a desired circuit pattern with a PCB processing machine.
The PCB processing machine has a work table on which the PCB substrate is set, and a work head provided with an X-axis, Y-axis and Z-axis driving devices for moving the work head in the longitudinal, lateral and vertical direction, respectively. The work head has a spindle provided with a chuck on which various cutting tools are attached. An index table is disposed under the=work table for storing the cutting tools and exchanging them when the spindle is lowered.
In a conventional PCB processing machine, a PCB substrate is positioned and fixed on the work table by suction. Thereafter, the portions of the copper conductive film excluding the portion which form the circuit pattern determined in accordance with the CAD data, are removed, holes pierced, and the contour of the board cut out, with respective appropriate cutting tools, in that order.
After the circuit pattern and holes are formed, and the contour shaped, a split pin SP (FIG. 9) is inserted in the hole and soldered to the circuit pattern at the ends, thereby providing conduction as well as fixation there-between. The split pin SP is made of a rectangular resilient metallic plate rolled to form a C in section. The side edges of the plate are cut into waveforms so that a wave-shaped slit S are formed in the pin. The upper and lower end portions are beveled for the ease of insertion. In order to improve the soldering ability and resilience, the split pin SP is made of a copper alloy containing phosphorous and bronze, plated with tin or solder. The outer diameter of the pin is in a range between 0.3 to 2 mm. The length, which depends on the thickness of the PCB substrate, is in a range between 2.5 to 3.5 mm in the case where the thickness of the PCB substrate is 1.6 mm. The thickness of the plate of the split pin SP is usually in the range between 0.1 to 0.15 mm.
These split pins are usually inserted in the holes formed in the PCB substrate with a tapered jig by manual operation, so that the manufacturing efficiency is rather poor. Moreover, the split pin SP is so small that it is difficult to accurately select the pin having the right diameter for each of the holes and to insert the pin a predetermined depth. More particularly, in a PCB where electronic devices are mounted over the pins, the length of the pin and the inserting depth must be carefully chosen so that the operation is further complicated.
Creamlike solder (solder paste) is applied by the upper end of the split pin SP when soldering other devices which are mounted on the PCB substrate. At the lower end, solder is applied by dip soldering. However, when an electronic device is mounted over the pin, it is necessary to solder before mounting by manual operation. In such a case, soldering iron is used in general. Since the split pin is small, it is difficult to apply an appropriate small quantity of solder and heat it with appropriate intensity. For example, the inner space of the split pin may be clogged with excessive solder, so that the advantages of having the throughholes are impaired.